Field of the Invention
The present invention relates to coating compositions and coating products made therefrom, containing modified inorganic nanoplatelets that form mesomorphic structure in a resin phase. The coating products exhibit low permeation/penetration properties, and can be used as anti-corrosion or barrier coatings.
Background Art
Metal corrosion is estimated to cost the U.S.A. $300 billion dollars annually.[1] A wide variety of anti-corrosion coating technologies have been developed to prevent or delay metal corrosion. However, the technologies that are known to be effective tend to cause undesirable side effects. For example, chromate-based coatings, which exhibit excellent corrosion resistance, are banned from usage in many applications because of their toxicity and carcinogenicity.[2] Zinc-based coatings are inconvenient as well due to their lack of ductility, high cost, and scarcity of raw materials.[3] Zeolites,[4, 5] ceramics,[6] and graphene[7, 8] have also been explored as corrosion-resistant coating materials, but show only limited success.
Recently, a new generation of organic coatings has attracted significant attention due to their facile and eco-friendly nature in fabrication and functionalization.[9-12] Strategies employed to prepare these new organic-based coatings include, but are not limited to, hydrophobicity-induced reduction in water accessibility,[13-15] passive oxidation-enabled metal protection,[16-18] and nanofiller-integrated corrosion inhibition.[19-22] However, the methodologies for preparing these new organic coatings usually involve complex chemistries and processes, making them difficult for large-scale commercial implementation. New anti-corrosion organic coatings that utilize existing industrial practices, such as spray coating, are rigorously sought after.
Plate-like nanostructures, such as graphene and its derivatives and clay, are impermeable to gases and moisture.[23, 24] Therefore, nanocomposite coatings containing 2D plate-like nanostructure have been reported to improve the corrosion resistance of metals.[18-21] It has been found that barrier properties of these protective coatings strongly depend on the nanoplatelet aspect ratio, volume fraction, dispersion level, and particularly the degree of alignment of the fillers.[25, 26] Inspired by highly aligned platelet-based lamellar structures observed in natural materials, such as nacre.[27] several assembly techniques have been developed to fabricate polymer/clay nanocomposites with similar lamellar structure, such as Layer-by-Layer (LbL) assembly,[28] ice templating and sintering of ceramics,[29] vacuum-assisted self-assembly,[30] electrophoretic deposition,[31] and air/water interface assembly.[32, 33] However, most of the above approaches share the limitations of requiring time-consuming sequential depositions or extensive energy consumption, which severely hinder their large-scale applications.